Power unit mount structures for vehicles or vessels designed for attached to a vehicle or vessel body at two portions thereof are known as disclosed, for example, in Japanese Patent Laid-open Publication No. HEI-10-238578.
The disclosed power unit mount structure, as illustrated here in FIGS. 9A and 9B, comprises a vibration isolating device or isolator 100 composed of a lower mounting bracket 101, a mount body 103 carried on the lower mounting bracket 101 via a rubber cushion 102, an upper mounting bracket 104 crimped to an upper end of the mount body 103 and supporting thereon a bolt 105 for attachment to an engine (not shown), and an annular stopper plate 106 serving as a stop against displacement of the mount body 103 in an upward direction.
The annular stopper plate 106, as shown in FIG. 9B, has a pair of L-shaped legs 107, 107 disposed in diametrically opposed relation with each other about an axis of the bolt 105. The legs 107 each have an oblong hole 108 for the passage therethrough of a screw (not shown) used for securing each leg to a vehicle body (not shown). The legs 107 are laid over a pair of mounting flanges (not shown), respectively, of the lower mounting bracket 101 (FIG. 9A), with the oblong holes 108 of the legs 107 held in registry with oblong holes (not shown) formed in the non-illustrated mounting flanges of the lower mounting bracket 101. The legs 107 of the stopper plate 106 and the non-illustrated mounting flanges of the lower mounting bracket 101 are secured by two screws (not shown).
With this arrangement, when vibration isolator 100 is subjected to a force acting in a direction 109 perpendicular to a line passing through centers of the oblong holes 108, 108, the vibration isolator 100 as a whole is likely to tilt and hence becomes unstable because the lower mounting bracket 101 has no mounting flange extending in the same direction 109 as the force applied to the vibration isolator 100.
To deal with this problem, a modification may be considered wherein the lower mounting bracket further has one or two additional mounting flanges extending in a direction perpendicular to the line connecting the centers of the oblong holes 108 of the two existing mounting flanges. The additional mounting flange or flanges have oblong holes for the passage therethrough of screws so that the lower mounting bracket 101 can be secured by the screws to the vehicle body at three or four points. The modification, however, makes the lower mounting flange complicated in configuration and requires a corresponding number of additional screw and threaded hole sets, which incur an additional cost, increase the entire weight of the power unit mount structure, and requires additional space for installation.